Patent Grant
7588097
1. Field of the Invention
The present invention relates to a technique for reducing vibration in a power impact tool that linearly drives a tool bit in its longitudinal direction by a swinging mechanism
2. Description of the Related Art
A technique for reducing or alleviating vibration caused in an electric hammer drill with a swinging mechanism is disclosed in EP1000712. According to the known art, the swinging mechanism includes a swinging ring swinging in the axial direction of a rotating shaft by rotation of the rotating shaft driven by a motor. A tool bit is linearly driven by a tool driving mechanism connected to an upper end region of the swinging ring. In a vibration reducing mechanism in this known technique, a counter weight is connected to the lower end region in a position shifted about 180° in the circumferential direction from the connection between the swinging ring and the tool driving mechanism. The counter weight linearly moves by the swinging movement of the swinging ring and thereby reduces vibration caused during the operation.
The counter weight is disposed in a lower region apart from the swinging ring. Therefore, the vertical distance between the path of travel of the counter weight and the axis of the hammer bit is widened. As a result, when the tool driving mechanism and the counter weight are driven by the swinging ring, unnecessary vibration is caused by a couple around the horizontal axis that intersects with the axis of the rotating shaft. Further, because the counter weight linearly moves by the swinging movement of the swinging ring, loss of a striking energy of the tool bit may be caused by resistance of the sliding area.
Accordingly, it is an object of the invention to provide a technique for further improving the vibration reducing performance in a power impact tool that linearly drives a tool bit by using a swinging mechanism.
Above described object is achieved by a claimed invention. According to the invention, a representative power impact tool performs a predetermined operation on a workpiece by striking movement of a tool bit in its axial direction. The power impact tool includes a motor, a rotating shaft, a swinging member and a tool driving mechanism. The rotating shaft is disposed parallel to the axial direction of the tool bit and rotationally driven by the motor. The swinging member is supported by the rotating shaft and caused to swing in the axial direction of the rotating shaft by rotation of the rotating shaft. The tool driving mechanism is connected to an upper end region of the swinging member in the vertical direction that intersects with the axis of the rotating shaft. The tool driving mechanism is caused to linearly move in the axial direction of the tool bit by the swinging movement of the swinging member and linearly drives the tool bit.
According to the invention, a counter weight that reduces vibration caused in the axial direction of the tool bit during the operation is provided. The counter weight is disposed in a region higher than a lower end region of the swinging member in the vertical direction that intersects with the axis of the rotating shaft. Further, a lower end of the counter weight is connected to the lower end region of the swinging member. The counter weight extends upward from the connection between the counter weight and the swinging member and has a pivot point in the extending end portion. When the swinging member swings, the counter weight is driven by the swinging member and caused to rotate in the axial direction of the tool bit, thereby reducing vibration caused in the axial direction of the tool bit.
The manner of “higher than a lower end region” according to the invention may typically be defined by a state in which the center of gravity of the counter weight is located in a region higher than the lower end region of the swinging member. For example, the counter weight may be disposed between the lower end region and the upper end region of the swinging member, the counter weight may extend in a region lower than the lower end region of the swinging member, or the counter weight may end in a region higher than the upper end region of the swinging member.
The counter weight according to the invention may preferably be configured to be disposed on the outside of the swinging member in such a manner as to avoid interface with the swinging member. Preferably, the counter weight may generally U-shaped having an open top.
The counter weight is disposed in a region higher than the lower end region of the swinging member and connected to the lower end region of the swinging member. With this construction, the counter weight located nearer to the axis of the tool bit can be driven by the swinging member. Further, the vibration reducing function of the counter weight can be performed in an optimum manner by adjusting the timing at which the swinging member drives the counter weight so as to correspond to the timing of vibration caused during the operation. According to the invention, the counter weight is moved in a position nearer to the axis of the tool bit, so that unnecessary vibration by couple force can be reduced.
Further, according to the invention, because the counter weight rotates, the sliding resistance can be reduced and energy loss can be avoided or reduced. Further, compared with the known construction in which the counter weight is designed to linearly move, the supporting structure of the counterweight can be made simpler.
As another aspect of the invention, the pivot point of the counter weight may be located at a position higher than the axis of the tool bit. By such construction, the vertical displacement during rotation of the counter weight can be reduced. As a result, the occurrence of unnecessary vertical vibration can be reduced.
As another aspect of the invention, the counter weight may include a connecting part connected to the swinging member and extending upward and a weight part seeing as vibration reducing weight. Further, the connecting part and the weight part may be provided as separate members and thereafter integrally formed with each other. Therefore, in manufacturing the counter weight the shapes and configurations of the connecting part and the weight part can be properly set based on individual functions. Specifically, the connecting part can be easily formed as a thin plate member, for example, by sheet metal processing, and the weight part can also be easily formed into a block, for example, as a casting. As a result, the manufacturing cost can be reduced.
Further, while the weight required to reduce vibration is ensured on the weight part side, the connecting part can be made thinner, for example, by sheet metal processing. Thus, the counter weight can be reduced in weight as a whole, and the mass of the component parts other than the weight part can be reduced in weight. Therefore, the occurrence of unnecessary vibration by the movement of the counter weight can be reduced.
As another aspect of the invention, the connecting part may include right and left arms with respect to the longitudinal axis of the tool to extend upward from the lower end connected to the swinging member and past the side of the swinging member. The lateral distance between the extending end portions of the arms can be changed by elastic deformation of the arms. Further, the pivot point may include a stem that extends in a direction that intersects with the extending direction of the arms and a hole that is fitted onto the stem for relative rotation. One of the stem and the hole may be formed in the extending end portion of each of the arms, and the stem and the hole are engaged with each other by utilizing a movement of changing the distance between the arms by-deformation of the arms.
According to such construction, the stem and the hole are engaged with each other by utilizing a movement of changing the distance between the arms by deformation of the arms.
As another aspect of the invention, the power impact tool may further include a dynamic vibration reducer that reduces vibration caused during the operation of the tool bit. The dynamic vibration reducer may include a weight that is allowed to reciprocate in the axial direction of the tool bit with a biasing force of an elastic element being applied to the weight. The counter weight drives the weight of the dynamic vibration reducer via the elastic element when the counter weight rotates. With both the vibration reducing functions of the counter weight and the dynamic vibration reducer, a further higher vibration reducing effect can be obtained. Further, with the construction in which the weight of the dynamic vibration reducer is driven by utilizing rotation of the counter weight driven by the swinging member, it is not necessary to additionally provide a driving mechanism specifically designed for driving the weigh, so that simplification in structure can be realized.
Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.
Each of the additional features and method steps disclosed above and below may be utilized separately or in conjunction with other features and method steps to provide and manufacture improved power impact tools and method for using such power impact tools and devices utilize therein. Representative examples of the present invention, which examples utilized many of these additional features and method steps in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person skilled in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed within the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe some representative examples of the invention, which detailed description will now be given with reference to the accompanying drawings.
First representative embodiment of the present invention will now be described with reference to
The body 103 includes a motor housing 105, a gear housing 107 and a handgrip 109. The motor housing 105 houses a driving motor 111. The gear housing 107 houses a motion converting mechanism 113, a power transmitting mechanism 114 and a striking mechanism 115. The driving motor 111 is a feature that corresponds to the “motor” according to the present invention. The rotating output of the driving motor 111 is appropriately converted into linear motion via the motion converting mechanism 113 and transmitted to the striking element 115. Then, an impact force is generated in the axial direction of the hammer bit 119 via the striking mechanism 115. Further, the speed of the rotating output of the driving motor 111 is appropriately reduced by the power transmitting mechanism 114 and then transmitted to the hammer bit 119. As a result, the hammer bit 119 is caused to rotate in the circumferential direction. The driving motor 111 is started by depressing a trigger 109a disposed on the handgrip 109. In the description hereinafter, the side of the hammer bit 119 is taken as the front side, and the side of the handgrip 109 as the rear side.
The motion converting mechanism 113 includes a driving gear 121 that is rotated in a vertical plane by the driving motor 111, a driven gear 123 that engages with the driving gear 121, a rotating element 127 that rotates together with the driven gear 123 via an intermediate shaft 125, a swinging ring 129 that is caused to swing in the axial direction of the hammer bit 119 by rotation of the rotating element 127, and a cylindrical piston 141 that is caused to reciprocate by swinging movement of the swinging ring 129. The intermediate shaft 125 and the swinging ring 129 are features that correspond to the “rotating shaft” and the “swinging member”, respectively, according to the present invention. The intermediate shaft 125 is disposed parallel (horizontally) to the axial direction of the hammer bit 219. The outer surface of the rotating element. 127 fitted onto the intermediate shaft 125 is inclined at a predetermined angle with respect to the axis of the intermediate shaft 125. The swinging ring 129 is supported on the inclined outer surface of the rotating element 127 via a bearing 126 such that it can rotate with respect to the rotating element 127. When the rotating element 127 rotates, the swinging ring 129 is caused to swing in the axial direction of the hammer bit 119 and in a direction that intersects with this axial direction. The rotating element 127 and the swinging ring 129 rotatably supported on the rotating element 127 via the bearing 126 form a swinging mechanism.
Further, a swinging rod 128 is formed in the upper end region of the swinging ring 129 and extends upward (in the radial direction) from the swinging ring 129. The swinging rod 128 is loosely fitted in an engaging member 124 that is formed in the rear end portion of the cylindrical piston 141. The cylindrical piston 141 is slidably disposed within a cylinder 135 and driven by the swinging movement (a component in the axial direction of the hammer bit 119) of the swinging ring 129 so that it reciprocates along the cylinder 135.
The striking mechanism 115 includes a striker 143 and an impact bolt 145. The striker 143 is slidably disposed within the bore of the cylindrical piston 141. The impact bolt 145 is slidably disposed within the tool holder 137 and is adapted to transmit the kinetic energy of the striker 143 to the hammer bit 119. The striker 143 is driven by the action of an air spring caused within an air chamber 141a of the cylindrical piston 141 by means of sliding movement of the piston 141. Then, the striker 143 collides with (strikes) the impact bolt 145 slidably disposed within the tool holder 137 and transmits the striking force to the hammer bit 119 via the impact bolt 145. The cylindrical piston 141, the striker 143 and the impact bolt 145 are features that correspond to the “tool driving mechanism” according to the inventor.
The power transmitting mechanism 114 includes a first transmission gear 131 that is caused to rotate in a vertical pane by the driving motor 111 via the driving gear 121 and the intermediate shaft 125, a second transmission gear 133 that engages with the first transmission gear 131, a cylinder 135 that is cased to rotate together with the second transmission gear 133. The rotation driving force of the cylinder 135 is transmitted to the tool holder 137 and fit to the hammer bit 119 supported by the tool holder 137.
A vibration reducing mechanism 151 will now be described with reference to
As shown in
A cylindrical protrusion 129a is provided in the lower end region of the swinging ring 129 or in a position shifted about 180° in the circumferential direction from the connection between the swinging ring 129 and the cylindrical piston 141. Correspondingly, an engagement hole 153d is formed in the lower end portion 153a of the counter weight 153. The protrusion 129a of the swinging ring 129 is loosely engaged in the engagement hole 153d for free relative movement. Therefore, when the swinging ring 129 swings, the counter weight 153 is driven by the swinging movement (a component of movement in the axial direction of the hammer bit 119) of the swinging ring 129 and is caused to rotate in a direction opposite to the direction of the reciprocating movement of the cylindrical piston 141. Further, a clearance is provided between the inner surface of the counter weight 153 and the outer surface of the swinging ring 129 such that the counter weight 153 can rotate without interfering with the swinging ring 129.
Operation of the hammer drill 101 of the first embodiment constructed as described above will now be explained. When the driving motor 111 (shown in
When the first transmission gear 131 is caused to rotate together with the intermediate shaft 125, the cylinder 135 is caused to rotate in a vertical plane via the second transmission gear 133 that engages with the first transmission gear 131, which in turn causes the tool holder 137 and the hammer bit 119 held by the tool holder 137 to rotate together with the cylinder 135. Thus, the hammer bit 119 performs a hammering movement in the axial direction and a drilling movement in the circumferential direction, so that the processing operation (drilling operation) is performed on the workpiece.
The hammer drill 101 can be switched not only to hammer drill mode in which the hammer bit 119 performs a hammering movement and a drilling movement in the circumferential direction, but to drilling mode in which the hammer bit 119 performs only a drilling movement or to hammering mode in which the hammer bit 119 performs only a hammering movement.
In the above-described processing operation, the counter weight 153 reduces impulsive and cyclic vibration caused in the axial direction of the hammer bit 119. The counter weight 153 is connected to the swinging ring 129 in a position shifted about 180° from the connection between the swinging ring 129 and the cylindrical piston 141 in the circumferential direction. Therefore, when the cylindrical piston 141 slides within the cylinder 135 toward the striker 143, the counter weight 153 rotates in a direction opposite to the sliding direction of the striker 143. Specifically, according to this embodiment, when the cylindrical piston 141 linearly moves toward the striker 143, and the hammer bit 119 is caused to perform a striking movement via the striker 143 and the impact bolt 145, the counter weight 153 rotates on the stem 153c in the axial direction of the hammer bit 119 and in a direction opposite to the cylindrical piston 141. In this manner, vibration cause in the hammer drill 101 in the axial direction of the hammer bit 119 can be reduced.
According to this embodiment, the counter weight 153 is disposed in a region higher than the lower end region of the swinging ring 129 and with this construction, the center of gravity of the counter weight 153 can be located nearer to the axis of the hammer bit 119 compared with the known art. As a result, unnecessary vibration can be reduced which may be caused by a couple around the horizontal axis that intersects with the axis of the intermediate shaft 125 when the cylindrical piston 141 and the counter weight 153 are driven by the swinging ring 129 in opposite directions.
Further, according to this embodiment, the counter weight 153 rotates in the axial direction of the hammer bit 119 on the stems 153c on the extending ends of the upwardly extending arms 153. The counter weight 153 is thus caused to rotate by the swinging movement of the swinging ring 129. Therefore, the sliding resistance of the sliding area can be reduced, so that loss of the driving force of sting the hammer bit 119 can be avoided or reduced. Further, the structure of supporting the counter weight 153 is formed by the stems 153c and the front and rear support plates 107b that rotatably support the stems 153c. Thus, the structure of supporting the counter weight 153 can be made simpler, compared with the construction in which the counter weight 153 reciprocates.
Further, in this embodiment the structure of connecting the counter weight 153 and the swinging ring 129 is realized by the construction in which the protrusion 129a of the swinging ring 129 is loosely engaged in the engagement hole 153d for free relative movement. Therefore, the lateral swinging movement of the swinging ring 129, or the swinging movement (shown by the arrow in
Now, the vibration reducing mechanism 151 according to a second representative embodiment of the present invention is explained with reference to
As shown in
The arms 163b of the counter weight 163 extend upward to a position higher than the axis of the intermediate shaft 125 and firer to a position slightly higher than the axis of the hammer bit 119. A stem 163c is founts on the extending end of each of the arms 163b and protrudes generally horizontally outward. The stem 163c is rotatably supported by a front support plate (not shown) on the gear housing 107 and a rear support plate 107b disposed on the inner housing 107a of the gear housing 107. Further, a weight concentration part 163e for concentrating the weight is provided genially in the middle of the arms 163b of the counter weight 163 in the extending direction. With this weight concentration part 163e, the center of gravity of the counter weight 163 is located nearer to the axis of the hanker bit 119 than that of the counter weight 153 of the fist embodiment.
According to this embodiment, like the first embodiment, in the processing operation, the counter weight 163 serves to reduce impulsive and cyclic vibration caused in the axial direction of the hammer bit 119. The counter weight 163 is connected to the swinging ring 129 in a position shifted about 180° from the connection between the swinging ring 129 and the cylindrical piston 141 in the circumferential direction. Therefore, when the cylindrical piston 141 slides within the cylinder 135 toward the striker 143, the counter weight 163 rotates in a direction opposite to the sliding direction of the striker 143. Specifically, according to this embodiment, when the cylindrical piston 141 linearly moves toward the striker 143, and the hammer bit 119 is caused to perform a striking movement via the striker 143 and the impact bolt 145, the counter weight 163 rotates on the stem 163c in a direction opposite to the cylindrical piston 141 in the longitudinal direction of the hammer bit 119. In this manner, vibration caused in the hammer drill 101 in the axial direction of the hammer bit 119 can be reduced.
In this embodiment, as described above, the weight concentration part 163e is provided on the arms 163b of the counter weight 163, so that the center of gravity of the counter weight 163 is located nearer to the same level as a horizontal plane including the axis of the hammer bit 119. As a result, unnecessary vibration can be reduced which may be caused by a couple around the horizontal axis that intersects with the axis of the intermediate shaft 125 when the cylindrical piston 141 and the counter weight 163 are driven by the swinging ring 129 in opposite directions.
When the counter weight 163 rotates on the stem 163c in the axial direction of the hammer bit 119, the counter weight 163 moves by a displacement X in the vertical direction that intersects with the axial direction of the hammer bit 119. In such a case, because the pivot point of the counter weight 163 is located at a higher position than the axis of the hammer bit 119, the vertical displacement X of the rotating counter weight 163 can be reduced. Therefore, the occurrence of unnecessary vibration by the vertical displacement can be reduced.
Third representative embodiment of the present invention is now explained with reference to
In this embodiment, the dynamic vibration reducer 171 includes a cylindrical body 172 that extends in the axial direction of the hammer bit 119, a vibration-reducing weight 173 disposed within the cylindrical body 172, and biasing springs 177 disposed on the front and rear sides of the weight 173. Each of the biasing springs 177 is a feature that corresponds to the “elastic element” according to the present invention. The biasing springs 177 exert a spring force on the weight 173 toward each other when the weight 173 moves in the longitudinal direction of the cylindrical body 172 (in the axial direction of the hammer bit 119). Further, an actuation chamber 176 is defined on the both sides of the weight 173 within the cylindrical body 172 of the dynamic vibration reducer 171. The actuation chamber 176 communicates with the outside of the dynamic vibration reducer 171 via a vent 172a (see
The counter weight 153 not only has a function of reducing vibration, but also inputs an excitation force in order to actively drive and forcibly excite the weight 173 of the dynamic vibration reducer 171. Specifically, in addition to the construction described in the first embodiment, an operating piece 153e is provided on the protruding end of each of the stems 153c of the counter weight 153 and rotates together with the associated stem 153c. The operating piece 153e protrudes forward, and the protruding end of the operating piece 153e is in contact with the back of the slider 155 which is slidably disposed within the cylindrical body 172 of the dynamic vibration reducer 171. The slider 155 supports one end of one of the biasing springs 177. Therefore, when the counter weight 153 rotates toter with the stem 153c, the operating piece 153e rotates together with the associated stem 153c, and the protruding end of tie operating piece 153e moves the slider 155 in a direction of pressing the biasing spring 177. Further, the counter weight 153 has the same construction as in the first embodiment, and is therefore given the same numeral and will not be described.
Further, the slider 155 has a cylindrical shape elongated in the direction of movement and having a closed end in the direction of movement. Therefore, the slider 155 can have a wider sliding contact area without increasing the longitudinal length of the cylindrical body 172. Thus, the movement of the slider 155 in the longitudinal direction can be stabilized.
In the third embodiment constructed as described above, in the processing operation, not only the counter weight 153 serves to reduce impulsive and cyclic vibration caused in the axial direction of the hammer bit 119 like in the first embodiment, but also the dynamic vibration reducer 171 disposed in the body 103 has a vibration reducing function. Specifically, the weight 173 and the biasing springs 177 serve as vibration reducing elements in the dynamic vibration reducer 171 and cooperate to passively reduce vibration of the body 103 of the hammer drill 101 on which a predetermined external force (vibration) is exerted. In this manner, vibration of the hammer drill 101 can be effectively reduced.
Further, when the hammer drill 101 is driven, the cylindrical piston 141 linearly moves toward the striker 143 by swinging movement of the swinging ring 129, and the hammer bit 119 is caused to perform a striking movement via the striker 143 and the impact bolt 145. At this time, like in the first embodiment, the counter weight 153 rotates on the stem 153c in a direction opposite to the cylindrical piston 141 in the axial direction of the hammer bit 119. In this manner, vibration caused in the hammer drill 101 in the axial direction of the hammer bit 119 can be reduced.
Further, when the counter weight 153 rotates on the stems 153c in the axial direction of the hammer bit 119, as shown in
As described above, according to this embodiment, the counter weigh 153 and the dynamic vibration reducer 171 are used in combination. Therefore, with both the vibration reducing functions of the counter weigh 153 and the dynamic vibration reducer 171, a further higher vibration reducing effect can be obtained.
Particularly in this embodiment, the operating piece 153e is disposed on the counter weight 153 provided for vibration reduction, and the operating piece 153e drives the slider 155 and inputs an excitation force to the dynamic vibration reducer 171. With this construction, it is not necessary to additionally provide an operating mechanism specifically designed as a means for inputting the excitation force, so that simplification in structure can be attained.
The vibration reducing mechanism 151 according to a fourth representative embodiment of the present invention is now explained with reference to
As shown in
A circular engagement hole 183d is firmed in the lower end portion 183a of the alms 183b. The protrusion 129a extends downward from the lower end region of the swinging ring 129 and is loosely engaged in the engagement hole 183d for free relative movement. Thus, the arms 183b are connected to the swinging ring 129. Further, the arms 183b extend upward past the side of the swinging rig 129 and to a position slightly higher than the axis of the hammer bit 119. A circular stem hole 183c is formed through the extending end portion of each of the arms 183b. The stem holes 183c are rotatably engaged with stems (bosses) 106d of a weight supporting portion 107c formed on the inner housing 107a. Thus, the counter weight 183 can rotate on the stems 106d in the axial direction of the hammer bit 119. The stems 106d and the stem holes 183c are features that correspond to the “stem” and the “hole”, respectively, according to the present invention.
The arms 183b are shaped into a predetermined fom, or generally U-shaped having the engagement hole 183a in the lower end portion 183a, the stem holes 183c in the extending end portions of the arms, and a plurality of weight mounting holes 183f generally in the middle of the arms in the extending diction, by sheet metal processing such as cutting, bending and hole making. The distance between the opposed extending end portions of the arms 183b can be changed by elastic deformation of the arms 183b. Therefore, assembly of the counter weight 183 to the weight supporting portion 107c of the inner housing 107a, or engagement of the stem holes 183c of the arms 183b with the stems 106d of the weight supporting portion 107c can be achieved by utilizing deformation of the arms 183b as shown in
According to the fourth embodiment constructed as described above, in hammering operation using the hammer drill 101, the counter weight 183 performs a function to reduce impulsive and cyclic vibration caused in the axial direction of the hammer bit 119. Thus, the same vibration-reducing effect can be obtained with the vibration reducing mechanism 151 as in the first and second embodiments.
According to the fourth embodiment, the arms 183b and the weight concentration parts 183e are formed as separate members. Therefore, in manufacturing the counter weight 183, the shapes and configurations of the arms 183b and the weight concentration parts 183e can be properly set individually in consideration of individual functions.
The arms 183b to transmit the movement of the swinging ring 129 to the counter weight 183 is formed by sheet metal processing, so that the arms 183b can be made thinner and thus lighter in weight while ensuing the strength required to transmit the movement of the swinging ring 129. As for the weight concentration parts 183e, the weight required to reduce vibration caused during operation can be readily ensured. As a result, the vibration reducing effect can be optimized while the counterweight 183 is reduced in weight as a whole. Further, by mass reduction of the component parts other than the weight concentration parts 183e, unnecessary vibration can be reduced which may be caused by movement of the counter weight 183. Further, the manufacturing cost of the counter weight 183 can be reduced with the arms 183b made of sheet metal.
Further, according to the fourth embodiment, the arms 183b can be assembled to the stems 106d of the weight supporting portion 107c on the body side by utilizing deformation of the arms 183b. Specifically, a biasing force is applied to the arms 183b in a direction that widens the distance between the opposed arms 183b, and the stem holes 183c are aligned to the stems 107c. Thereafter, the force is released, so that the stem holes 183c can be fitted onto the stems 106d. Thus, the assembling operation can be easily performed. Further, with the construction in which the counter weight 183 is assembled by utilizing deformation of the arms 183b, the counter weight 183 as a whole can be made compact. Further, the arms 183b forming the stem holes 183c need not have a two-part structure having front and rear section&. Thus, simplification in structure can be attained.
Further, in the above-described embodiments, the swinging ring 129 of the swinging mechanism is described as being supported for relative rotation at a predetermined inclination angle by the intermediate shaft 125 and caused to swing in the axial direction of the intermediate shaft 125 when the intermediate shaft 125 rotates. However, the construction of the swinging mechanism is not limited to this. Specifically, the swinging ring 129 may be mounted such that it is inclined at a predetermined angle with respect to the axis of the intermediate shaft and rotates together with the intermediate shaft. Thus, the swinging mechanism may be constructed such that the swinging ring is caused to swing in the axial direction while rotating together with the intermediate shaft when the intermediate shaft rotates. Further, in the above-described embodiments, the hammer drill 101 is described as an representative example of the power impact toot but the present invention can be applied not only to the hammer drill 101 but also to a hammer which performs only hammering operation.
Further, in the fourth embodiment, the stem holes 183 may be formed on the arm support portion 107c side, and the stems 106d on the arms 183b side.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-228231 | Aug 2006 | JP | national |
| 2007-178594 | Jul 2007 | JP | national |
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| Number | Date | Country | |
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| 20080047723 A1 | Feb 2008 | US |
